How To Listen To The Aurora Borealis

Laboratory tests reveal that a surprising variety of substances, including frizzy hair and vegetable matter, can act as radio-to-audio VLF transducers. Credit: NASA

I wasn’t just watching this weekend’s aurora display but listening to it, too. No, I didn’t hear the ‘swishing’ or ‘crackling’ reported by some. Despite seeing hundreds of displays ranging from meek to wild, I’ve yet to actually hear any auroral audio. There is some evidence however that electrophonic transduction can convert otherwise very low frequency (VLF) radio waves given off by the aurora into sound waves through conductors. Wire eyeglass frames, grass and even hair can act as transducers to convert radio energy into low-frequency electric currents that can vibrate an object into producing sound. Similar ‘fizzing’ sounds have been recorded by meteor watchers that may happen by the same process.

The WR-3 VLF receiver with headphones. Photo: Bob King

Of course another reason people might hear auroras is they imagine a soundtrack. It’s a psychological thing – you see a spectacular display of auroral light and in your head hear sounds your imagination might expect like crackling and whooshing. Given that the aurora is never closer to the ground than 50 miles, the air is far too thin to transmit any weak sound waves that might be produced to your ears.

If you’re like me and hard of auroral hearing, a small VLF radio receiver will do the job nicely. This handheld device converts very low frequency radio waves produced from the interaction of the solar electrons and protons with the Earth’s magnetic field into sounds you can listen to with a pair of headphones.

We’re used to waves of light which are very, very short, measuring in the millionths of an inch long. The pigments in our retinas convert these waves into visible images of the world around us. Radio waves given off by auroras and other forms of natural ‘Earth energy’ like lightning range from 19 to 1,800 miles long or longer! To make them available to our senses we use a radio receiver. I fire up a little unit called a WR-3 that I bought for $60 back in the mid-1990s. The components are housed in a small metal box with a whip antenna and powered by a 9-volt battery. The on-off switch also controls the volume. Plug in a set of headphones and you’re ready to listen. That’s all there is to it.

A rural location is ideal for listening to the subtle sounds of the aurora with a VLF radio. Just turn it on and hold it up to the sky.This photo was taken early Saturday morning when green auroras were still visible through breaks in the clouds. Photo: Bob King

The receiver picks up lots of things besides aurora including a big ‘unnatural’ hum from alternating or AC current in power lines and home appliances. It creates a loud, continuous buzz in the headphones. You’ll need to be at least a quarter mile from any of those sources in order to hear the more subtle music of the planet. I drive out to a open ‘radio quiet’ rural area, turn on the switch and raise the antenna to the sky. Don’t stand under any trees either. They’re great absorbers of the low frequency radio energy you’re trying to detect.

The magnetosphere of the Earth is enormous bubble of magnetism that surrounds our planet. It's created through the interaction of the solar wind and Earth's magnetic field. The magnetosphere acts as a shield to protect us from dangerous radiation in space. Credit: NASA

The first thing you hear will be the pops, crackles and sizzles of distant lightning called sferics which are similar to what you’ve probably heard on your car radio during a thunderstorm.

Lightning gives off lots of energy in the long end of the radio spectrum. When that energy gets ducted through the upper layers of Earth’s atmosphere called the ionosphere over distances of several thousand miles, it emits another type of sound called ‘tweeks‘ which remind a listener of pings or dripping water. Flurries of tweeks have an almost musical quality like someone plucking the strings of a piano.

Lightning produces a great variety of radio 'sounds' you can hear with the right receiver. Credit: Mircea Madau

When those same lightning radio waves enter Earth’s magnetosphere and interact with the particles there, they can cycle back and forth between the poles traveling tens of thousands of miles to create what are called whistlers. These things sound really eerie. After their long journey, the higher frequency waves arrive before the lower frequency ones causing them to spread out in tone. What you hear are a series of descending whistles that remind me of the whistling sound of bombs released from a plane like you’d see in a World War II movie. Tweeks are very brief; whistlers last anywhere from 1/2 to 4 seconds or longer.

Sometimes you’ll hear dozens of whistlers one after the other. There there’s the aurora. When conditions are right, a VLF receiver can pick up disturbances in Earth’s magnetic bubble spawned by auroras called ‘chorus‘ or ‘dawn chorus’. Talk about strange. Sometimes there are swooshing sounds, but chorus primarily sounds like a pond full of peeping frogs or a flock of birds singing at sunrise. Click on the links above to hear the different sounds.

An active auroral display sounds like a chorus of chirping birds through a VLF radio. Photo: Bob King

Saturday night was a bonanza for natural radio. I heard all the phenomena described above. A line of passing thunderstorms provided a bounty of crackles and tweeks early on. As they thunderheads drifted far to the east, whistlers were heard a couple seconds after the appearance of every distant lightning flash. Most of these lasted 3 to 4 seconds, meaning they’d traveled back and forth between Earth’s magnetic poles. How astonishing it was to sense our planet’s magnetosphere through sound.

When the aurora was strongest starting around 1 a.m., the chorus rose from the background noise of lightning sferics and burbled and chirped along for nearly an hour. Later, through the aurora was still active, the sounds mysteriously disappeared.

I realize this radio stuff may not be everyone’s piece of pie, but if you’re interested in listening to VLF and in particular the aurora, basic receivers are available through at least several online sites shown below. I’ve only used the WR-3 and can’t speak for the others, but they all run around $125. Oh, and by the way, don’t use one when there’s a lightning storm nearby. Holding a metal aerial under a thundercloud is not recommended!

More on natural radio can be found HERE. Things to keep in mind when considering a purchase are whether you have access to an open area 1/2 mile from a power line and away from homes. You’ll also need patience. Many nights you’ll only hear lightning crackles from distant storms thousands of miles away peppered by the occasional ping of a tweet. Whistlers may not appear for weeks at a time and then one night, you’ll hear them by the hundreds. But if you regularly watch the sky, it’s so easy to take the radio along and ‘give a listen’ for some of the most curious sounds you’ll ever hear. It’s just one more way to be in touch with the home planet.

Hello! About 33 years ago, in Kingsville, Ontario (Canada’s most southerly town), I was coming home very late one winter evening. As I stood on the porch facing the house, I heard a swishing and crackling behind me so I turned to see flashes of silver Aurora Borealis that lasted for quite a long time. I had never before heard of anyone seeing them that far south, nor have I since. I had no idea that sound came with them, so I was not predisposed to image this… in fact, had I not heard the sounds, I would not have turned around to see them. I was wearing no glasses or jewellery and was not carrying a battery radio or any such thing. (Cell phones had not been invented.) When I told someone from Northern Manitoba, they said, “Of course, the Aurora Borealis makes wonderful sounds!”

Very informative.I was just having a conversation about if the NL’s make sounds with friends on FB.I believed not. Since I’d seen them countless time in Alaska and here in Washington St. One girl said she could hear what sounded like people talking every time the NL were strong over head.She was wondering if there Big metal garage could conduct the sounds. Also said there was power lines and large transformer close by.After ready you artical I’m guessing the transformer mabey.I posted your arrival on my Facebook. I now want to go get the listening device you spoke of. Thank You. Glen Leighton Belfair WA.